The present invention relates to an apparatus and a method for filling a space surrounded by a housing or casing with an inert gas and forming a desired gas atmosphere in the space.
For example, in a batch-type low-pressure CVD apparatus, a number of wafers are placed in a casing and a desired film is formed on a surface of each wafer by chemical vapor deposition. The wafer surface must be protected against oxidation due to oxygen or moisture contained in the ambient atmosphere, so as to prevent an oxide film from being formed on the wafer surface.
To this end, conventionally, as shown in FIG. 1, a dry inert gas G is introduced through a gas introduction opening 3 into a space 2 surrounded by a casing 1, and particles are removed from the gas by means of a particle-removing filter (such as an HEPA or ULPA filter) 4, to thereby form a dry, inert gas atmosphere in the space 2 and prevent the above-mentioned oxidation. At the same time, the gas is discharged from the space 2 through a discharge opening 5 at a predetermined flow rate, thus preventing contamination of the gas contained in the space.
Thus, in such a system as mentioned above, an inert gas is used in a large amount, so that a running cost becomes inevitably high.